Method and apparatus for producing improved conductor cables



0. HAUGWITZ Nov. 6, 1962 2 Sheets-Sheet 1 Filed March 25, 1958 \MKwou QW'MM l A 1% n 7 wow H 1/ l; m. N lllllllllllllllllllllllllllllll Ill ||l|l| Ill rul lllll O. HAUGWITZ Nov. 6, 1962 METHOD AND APPARATUS FOR PRODUCING IMPROVED CONDUCTOR CABLES 2 Sheets-Sheet 2 Filed March 25, 1958 mm 1 [3 H 6A N\ 4. P. .w\ bk .m m Q mum MN EN H \\\.8 2%) N K 8 N ow III M kh v N 7% Q E @N & H A um i L R M -1 6 m h v m w w W w 4 N Na 3 NR x NN s% w. v m u u N Mk United States Patent Ofiice 3,061,997 Patented Nov. 6, 1962 METHOD AND APPARATUS FOR PRODUCING IMPROVED CONDUCTOR CABLES Otto ll-llaugwitz, La Celle Saint Cloud, France, assignor to Societe Anonyme Geoifroy-Delore, Paris, France, a French company Filed Mar. 25, 1958, Ser. No. 723,757

Claims priority, application France Mar. 26, 1957 9 Claims. (Cl. 57-5852) This invention relates to the manufacture of flexible multi-strand assemblies such as wire rope, cables, and the like, and is especially concerned with the production of electric cable conductors comprising a relatively large number of individual wires or strands.

In the production of such cable assemblies the strands may be wound in separate layers, with adjacent layers being wound in opposite directions, or all the strands may be simultaneously twisted together with a common helical pitch and in a common direction. This latter method is sometimes known as throwing. The first above mentioned method results in a cable conductor having a perfectly smooth outer surface; however the method is slow and the output of machines operating in accordance with it is limited. Hence cable conductors produced in this way are expensive. Moreover, small feed-out reels have to be used.

The throwing process in turn can be subdivided since it may be performed as either a single-step or a two-ormore-step throwing process. In the single-step process a single twist is imparted to the strands; that is, all the strands are fed from a feed-out station to an input die or guide in which they are combined, and are then passed to a take-up sheave which is rotated .about an axis normal to the axis of the sheave, so as to impart the desired twist to all the strands simultaneously. The single-stage throwing process is convenient in that it imposes no limit on the size of feed-out reels used. It also permits winding the strands of the cable regularly in separate layers if desired. However its output is not substantially higher than that of the first method mentioned.

in single-step throwing machines, the feed-out reels supplying the individual strands or the take-up sheave for the completed cable are mounted for rotation and the reels or sheave complete one revolution each time the cable advances by an amount 17 if it is desired that the cable have a pitch p. It is readily appreciated that the production rate is limited by the maximum permissible rotation speed of the reels or sheave.

It is for this reason that two-step or multiple-step throwing machines have been designed, comprising generally a rotary frame and a sheave inside the frame to receive the cable which is twisted twice in succession for each rotation of the frame. Thus for a speed of rotation of the frame equal to that of the feed-out reels or sheave in a single-step machine, the cable is taken up at twice the rate for a same pitch p. Accordingly, a twostep throwing machine has normally twice the output of a single-step machine for a same speed of the rotating parts.

in twostep throwing processes, the strands are first pro-twisted by having a first twist imparted to them as the strands are passed from the input guide to a rotary frame and are then taken up on a stationary, intermediate, take-up drum or sheave mounted within the rotary frame. In a subsequent twisting stage, the pro-twisted strands are drawn out from said intermediate take-up drum by way of the rotary frame and are passed in reverse to be taken up at a final take-up station exterior of the machine, an additional twist being imparted to the strands during this second stage of the process. This two-stage throwing process permits high outputs. However it has been found that the resulting cable conductor is somewhat unsatisfactory in that the strands thereof are apt to lie in irregular configurations with the various strands continually crossing over. Smooth uniform layers cannot be obtained. The over-all outer diameter of the finished cable is larger than the sum of the diameters of the respective strands and is larger than the diameter of a cable made by the other processes mentioned from the same number of strands, so that more insulating and shielding material is required. Appearance is poor and objectionable internal strains are found to be present within the cable due to the irregular configuration of the strands.

The reason for this serious defect is that, during a throwing process involving strands arranged in a plurality of coaxial layers, the strands in different layers lie at different distances from the axis of the cable, so that the throwing process tends to shorten them by different amounts, the outermost layers tending to be shortened to greater degrees than the inner layers. The strands of the inner layers thus become too long and are forced to crop out from place to place on the outer surface in between the outer layers. This effect does not occur in a single-stage throwing process, or in the initial stage of a multi-stage process, because the strands at that time issue from the supplies provided by the feed-out reels and are supplied as fast as the demand therefor arises, using up differential lengths of strands in the inner and the outer layers. Of course this is not possible in the subsequent stages of the throwing process (where a two or more stage process is concerned) since the lengths of the strands are limited.

t is a chief object of this invention to provide an improved method of producing cables by a multi-stage throwing process. Other objects are to provide improved multi-strand cables conductors and the like, made by the multi-stage twisting processes described, which cables will be smoothly and regularly wound, will be free of outcroppings of inner strands, free of inner strains and stresses, and will have improved appearance.

Other objects relate to the provision of improved multistrand conductor cables and the like in which the helical pitch of at least some of the strands is cyclically varied along the length of the cable.

Thus the strands of successive layers, having either a constant pitch p or a variable pitch of average value p. are not substantially parallel to each other, thereby eliminating mutual intersecting of strands.

In accordance with an important aspect of the invention, the objectionable differential shortening of the strands in the inner and outer layer of a cable during the twisting or throwing operation, is compensated for by applying an axial draft force to the strands at two spaced points respectively before and beyond the point where the strands are being twisted together, the draft force applied beyond said point being equal to, or preferably slightly higher than, the draft force applied before said point, so as to impart a slight elongation to the strands and thus oppose the tendency of the strands to distortion as otherwise present due to the effect of the diiferent distances of said strands from the center of the cable, as explained above.

Owing to the application of the two draft forces both before and beyond the twisting area, the strands are positively prevented from slipping .and from shifting relatively to one another. It is found that the finished cable twisted in this way has full dimensional stability thereafter. Internal strains are stabilized. The difference in draft velocities imparted to the strands before and beyond the twisting area is so selected that the maximum permanent elongation imparted to the strands of the outermost layer of the cable remains well within the safe tensile range. The mechanical tensile characteristics of such a cable may, in fact, be improved owing to the prestressed condition of the strands.

It has been found that the advantageous results described above can also be achieved in a somewhat different manner; namely, by cyclically varying the helical pitch of the strands in some of the layers, alternately above and below the constant predetermined average helical pitch value of the other layers.

The invention will now be described with reference to the accompanying drawings wherein:

FIG. 1 is a chart illustrating the process responsible for the relative shortening of the outer layers of a cable conductor during a throwing or twisting operation;

FIG. 2 illustrates a double-twist two-stage throwing frame constructed in accordance with the invention;

FIG. 3 is a fragmentary plan view corresponding to FIG. 2;

FIG. 4 is a developed view illustrating the crossed relationship obtained between adjacent layers of a cable conductor in case of a transient change effected in the Pitch of one of the layers, according to a feature of the invention.

FIG. 5 is a cross-section of the cable.

Referring to FIG. 1, consider for example the case of a cable conductor comprising 37 strands laid out as follows; A central strand or core is surrounded by an innermost layer consisting of 6 strands, surrounded in turn by a l2-strand intermediate layer and then by an 18- strand outer layer. The diameters of the respective layers are designated by d d d respectively, see cross sectional view in FIG. 5. Further assuming that the pitch of the twisting process equals 15 times the over-all diameter of the conductor and that the twisting operation is performed in a single step, it is easily seen that the angle formed by each strand of any one layer with the axis of the conductor equals 10 in the l8-strand outer layer, 75 in the 12-strand central layer, 4 in the 6-strand inner layer and of course 0 for the central strand or core. In the case of a two-step throwing process, the first twisting step is performed with a pitch equal to twice the desired final pitch so that the corresponding values for the angle a then are 3.75 2 and 0 respectively. The relative shortening in the axial length of each layer with respect to the central strand equals 100 (l-cos a)%. In the present instance, the relative shortening effected in the respective layers during the initial twisting step would be respectively 0.38% for the l8-strand outer layer, 0.21% in the l2-strand intermediate layer and 0.06% in the 6-strand inner layer. However, during the initial twisting step the above shortening of the various. layers does not affect the characteristics of the conductor since the lengths of strand are supplied from the feed-out reels progressively as required, so that the respective strands are not subjected to any shortening or mechanical strains. On the other hand, during the second twisting Step, there no longer is any compensation for the differentials in length of the strands. Thus, between the outer layer and the central core, there remains a differential of shortening which results in a relative displacement of the strands with respect to one another within the cable.

It is seen from FIG. 1 that if the throwing pitch is selected equal to times the diameter of the cable, the rate of shortening between the first and second twisting steps assumes substantially higher values (0.76%, 0.62% and 0.08% for the respective layers). This in turn causes a still more marked disturbance in the inner arrangement of the strands.

The twisting method of the invention eliminates the shortening in the respective layers during the twisting steps subsequent to the initial twisting step. The method will be described with reference to FIG. 2 which illustrates the invention as embodied in a two-step, doubletwist throwing machine of a general type similar to that described in the co-pending application Ser. No. 708,802, now Patent No. 2,998,694.

In FIG. 2 there is illustrated such a machine supplied with individual wire strands 1 issuing from a feed-out reel station 2 supporting the feed-out reels of the respective strands. The center reel 2!: supplies the center strand. Six reels 2b equally spaced around the reel 2a supply the strands of the first layer. Twelve reels 2c equally spaced around the reels 2]) supply the strands of the second layer. Finally eighteen reels 2d equally spaced around the reels 2c supply the strands of the third layer. The drawing shows only the reels contained in the vertical axial plane of center reel 2a. The wires issuing from the respective feed-out reels are led through guides spaced circularly in distributor grille structures 3a, 3 and 4 so as to deliver the strands in generally concentric annular layers.

The guided strands are then assembled and twisted together into a cable as they pass through frames provided for that purpose. The first layer supplied from the reels 2b is assembled in a stationary frame f1 mounted at the center of grille 3. The strands of the second layer supplied from the reels 2c are assembled and twisted in a frame 22 which is reciprocated in a manner to be hereinafter described. Finally, the strands of the third layer supplied from the reels 2d are assembled and twisted in a frame f3.

The throwing machine only briefly described herein, comprises downstream of the assembling and twisting frames two spaced aligned bearings 5 and 6 in which the pivot shafts 7 and 8 of a rotary frame 9 are journalled, said frame being driven in rotation from a motor 18. Mounted within the frame 9 is a support 11 in which a pair of draft pulleys 12 are journalled. Iournalled in the support 11 coaxially with the rotary frame 9 is an intermediate take-up sheave 13 on which the pro-twisted cable is reeled. A reciprocatory feeder pulley 14 is provided for uniformly depositing the cable in regular coils along the length of the sheave or drum 13. The support 11 is held in a stationary condition by its own weight because its center of gravity is below the axis of bearings 5 and 6. The drum 13 is rotated and the reciprocatory feeder device 14 is reciprocated by suitable drive means including a friction coupling not shown, from the draft wheels 12.

Supported from the end shaft section 7 of the rotary frame and rotatable with it is a further dual draft-wheel arrangement 15.

Further driven from the shaft 7, with a drive ratio of /2, is the crown gear 16 of a differential gearing unit e A planetary bevel gear 17 meshing with the crown gear 16 is connected by a shaft a to a suitable gearing p1-p6 for driving the draft wheels 15. The gear 11 drives a gear p2 to which is secured for rotation therewith a gear p3 seen in FIGS. 2 and 3. The gear )3 meshes with a gear p4 keyed on the same shaft as a bevel gear p5. Gear p5 drives a further bevel gear 16 secured for rotation with one of the draft wheels 15. Similarly the other planetary bevel gear 18 of the differential unit 2 is connected to the draft wheels 12 through a shaft 11 and gearing p7 to p15.

The shaft a with gear p7 secured thereto drives gear p8 secured to gear p9 meshing with gear p10 keyed on the same shaft as gear [211. This gear 211 drives a gear p12. secured to a further gear p13 meshing with gear p14 keyed to the same shaft as bevel gear p15 meshing with bevel gear p16 keyed to the same shaft as one of the draft wheels 12.

A reverser clutch 19 is adapted to be driven from crown gear 16 in one direction during the first stage of the twisting process (i.e. from the feed-out station 2 to the intermediate take-up drum 13) and in the opposite direction from the crown gear 16a and gear e during the second stage of the process (from drum 13 to final take-up 21), and drives the planetary bevel gear 18 in a.

corresponding direction through a drive including variable ratio gears 20 for modifying the throwing pitch and a gear p17 meshing with the gear p7. The operation of the differential is such that both draft wheel systems 12 and are normally rotated at a common speed and in the same direction. This prevents any possibility of relative slippage between the layers when the second twist is imparted to the cable on issuing from the tube T of frame 9 over the pulley P before passing toward the draft wheels 12 and the sheave 113. The first twist clearly was imparted at the assembling and twisting stations before reaching the draft wheels 15. It is found that the completed multi-strand cable conductor retains its shape and dimensions indefinitely.

In the second twisting step, the cable conductor is passed in a reverse direction from drum 113 outwards and, in the exemplary installation shown, is finally received over a pulley in a stationary cylindrical barrel 21 where it is coiled.

In point of fact, the strands ll fed from the reels 2a to 2d are formed into a cable C of several layers twisted successively in the same direction by the grille structures 3m, 3 and 4, and by the frames f1, 22. and f3. The cable C issuing from the frame f3 passes over a guide pulley P2, is then wound several turns on the two draft wheels 15, passes over another guide pulley P3, then through the inside of the hollow shaft 7, over guide pulleys P4 and P5, through a hollow tube T mounted on the rotary frame 9, over guide pulleys P6 and P, and through the hollow shaft of the sheave 13, following which it is wound several turns on the two drafting wheels 12 and finally wound around sheave 13.

When the cable C is unwound from the sheave 13 it follows the same path in reverse as far as guide pulley P1 and then passes over pulley P7 into the barrel 21.

Assuming the twisting operation is effected with a pitch equal to 15 times the cable diameter, the degree of elongation imparted to the outer layer of strands is only 0.24%. Since the elastic yield point is on the order of 2%, it will be seen that there is no danger whatever of the tensile yield point being exceeded.

It is sometimes found desirable to arrange matters to that there will be a slight speed differential, of e.g. 2%, between the two draft systems 12 and 15. In such case all of the layers of the cable except the central core are subjected to some degree of tension and elongation, and at the output of the machine the twisted conductor sustains a uniform, over-all radial contraction of 2%. The permanent elongation thus sustained would be a maximum for a pitch value 12 times the diameter, and its value would then be 0.8% in the outermost layer, a wholly acceptable figure.

In the case of the exemplary conductor cable shown in FIG. 1, which can be described by the pattern (l+6+l2+18) indicating the numbers of strands in the respective layers it will be noted that the pitch of the l2-strand layer for example may be varied within the range extending from the pitch of the 6-strand layer to that of the l8-strand layer, so that it will be longer in some sections and shorter in others, although the average pitch should of course remain the same as in the remaining layers. The resulting cable will be of the type illustrated in the developed view of FIG. 4. In this figure one layer shown in dotted lines has a constant pitch throughout the length of the conductor while another layer shown in full lines has a cyclically modified pitch in the manner just indicated, with the pitch of the fullline layer being greater in the section between lines A and B, and smaller within the section from B to C. It will be seen that with this arrangement the two layers are regularly crossed over: Thus, the objectionable effects previously noted are again avoided, though in a different way.

In order to accomplish such a pitch variation in one of the layers of the cable, one possible method would 6 be to impart rotation to the distributor grills 3, 4 but obviously such a method would be limited since it would not be possible to impart more than one full revolution to the grids without entangling the strands ahead of them.

According to the present invention, any desired variation of pitch may be imparted to one or more layers of strands in a cable conductor or similar multi-strand assembly, over a length including one or more pitch iengths. For this purpose, the distributor grids 3 and 4 (PEG. 2) are spaced by a suitable amount and a reciproeatory movement is imparted to the die supporting structure 22. Thus, the point at which the strands of the layer under consideration are combined is caused alternately to move towards and away from the assembling point of the strands of the adjacent layer, thereby alternately shortening and lengthening the twisting pitch without however modifying the average pitch in the layer.

Various desirable cable configurations may be achieved in this way, one being that wherein all the odd layers (for instance) are cyclically varied in pitch while all the even layers are made to retain a constant pitch. The reciprocation of the frame 22 may be effected in any suitable way, e.g. by means of a roller g secured to the frame 22, slidable on rods t and riding in an endless helical cam groove formed in a drum 23 driven from the shaft 7 through suitable reduction gearing 24.

It should be noted that the feature last described may be if desired applied simultaneously with the first described feature involving elongation of the strands.

In order to avoid distorting the truly circular shape of the cable conductor due to pulling forces exerted as the conductor is passing around the various drive and draft pulleys, all such pulleys should be dimensioned with relatively large diameters, and the grooves should be so shaped as to conform accurately to the contour of the cable. Hence, such pulleys are preferably removably mounted so as to be readily interchangeable for use with cable conductors differing in cross section.

What I claim is:

1. In a method of producing a multi-strand cable-like assembly, the steps of twisting a plurality of strands together in a first and at least one further twisting area and simultaneously applying axial draft forces to said strands at two spaced points respectively before and beyond each said further twisting area, the draft force applied beyond said further area being not lower than the draft force ap plied before said further area thereby to oppose the tendency of said strands to distortion under the effect of the differential distances of said strands from the center of the cable-like assembly.

2. The method claimed in claim 1, wherein the draft force applied beyond said further area is slightly higher than the draft force applied before said further area thereby to tend to elongate the strands between said points.

3. In a method of producing a cable-like assembly including at least two coaxial layers, each consisting of a plurality of helically wound strands, the steps of twisting said strands together in a first and at least one further twisting area and simultaneously applying axial draft forces thereto at spaced points respectively before and beyond said further area, the draft force applied beyond said further area being slightly higher than the force applied before said further area thereby to counteract the tendency to radial expansion of the helices formed by the strands, under the effect of the differential distances of said layers from the axis of the cable-like assembly.

4. A method of manufacturing a multi-strand cable assembly in at least two steps which comprises, in a first step pre-twisting the strands together at a pro-twisting area while applying an axial draft force to the strands beyond said area in a first direction, taking up the pre-twisted cable at an intermediate station, then in a second step further twisting said strands while applying a first axial draft force in a direction opposite to said first direction at a first point ahead of the point where the strands are being further twisted, and a second axial draft force at a second point beyond said last-mentioned point, with said second draft force being in the same direction and being at least equal to said first draft force, thereby to impart slight elongation to said strands during the further twisting step.

5. A throwing machine for producing a multi-strand cable, which comprises a rotary frame for twisting an assembled plurality of strands together at a common twisting station, and two separate draft units engaging said assembled strands at two draft stations respectively before and beyond said twisting station in the direction of cable feed for imparting positive axial velocities to said assembled strands, and means coupling said draft units for imposing a predetermined constant ratio between said velocities which ratio is slightly greater than unity thereby to impart slight elongation to said strands between said draft stations.

6. A twisting machine for producing a multi-strand cable, which comprises a feed-out station for feeding a plurality of strands, an input guide for combining said strands, a rotary frame receiving the combined strands to pre-twist them, an intermediate take-up station within said rotary frame adapted to take up the pre-twisted strands, a first draft pulley system engaging said strands between said input guide and said rotary frame, a second draft pulley system engaging said strands between said rotary frame and said intermediate takeup station, and coupling means for driving both draft pulley systems at correlated velocities, and means for reversing the direction of drafting of said pulley systems.

7. A twisting machine as claimed in claim 6, wherein said coupling means comprise differential gearing having a crown gear and planetary gears, means rotatively connecting said crown gear with said rotary frame, means rotatively connecting said planetary gears With said respective draft pulley systems, and means for imparting additional drive to one of said planetary gears.

8. in a throwing machine as claimed in claim 5, the provision of draft and guide pulleys with grooves conforming in size to the particular size cable being manufactured, and means for interchangeably mounting said pulleys.

9. A throwing machine for producing a multi-strand cable, which comprises a rotary frame for twisting an assembled plurality of strands together at a common twisting station, and two separate draft units engaging said assembled strands at two draft stations respectively before and beyond said twisting station in the direction of cable feed for imparting positive axial velocities to said assembled strands, and means coupling said draft units for imposing a predetermined constant ratio between said velocities which ratio is slightly greater than unity thereby to impart slight elongation to said strands between said draft stations, wherein each draft unit comprises at least one pulley about which said strands are trained whereby rotation of said draft pulleys will impart said axial velosities to the strands, and said coupling means include differential gearing having differential elements respectively coupled to said respective draft pulleys.

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